Despite the currently available drug therapies, cardiovascular diseases remain one of the major causes of ill health in the western world. The identification of additional therapeutic targets, such as G-protein-coupled receptors (GPCR), that may modulate the pathological state has been of interest. Following its desorphanisation, the urotensin II receptor, initially termed sensory epithelium neuropeptide-like receptor or GPR14, has been studied for its implication in the cardiovascular homeostasis in either health or disease state.[1]
Initially isolated more than 20 years ago from the caudal neurosecretory system of teleost fish, urotensin II (UII) has been subsequently characterized in several species including human.[2] This highly conserved cyclic peptide exerts a broad spectrum of biological actions in mammals including the modulation of cardiorenal, pulmonary, central nervous systems, and endocrine functions. Urotensin II has been characterized as an important mediator of the cardiovascular function and has been involved in vasculoprotective and vasculopathic effects. As a matter of fact, concentrations of UII and UII mRNA were reported to be elevated in patients suffering from atherosclerosis, heart failure, hypertension, pre-eclampsia, diabetes, renal disease and liver disease.
UII has been described as the most potent endogenous vasoconstrictor to date, being up to 2 orders of magnitude more potent than endothelin-1 (ET-1), another very potent vasoconstrictor.[3] Recent work in mammals revealed the existence of a second gene encoding a precursor of a UII paralog, called UII-related peptide (URP).[4] This octapeptide, identified in humans, mice and rats, also comprises the highly conserved cyclic hexapeptide core sequence (CFWKYC) (SEQ ID NO: 92) found in UII. However, these peptides differ in the length and composition of their N-terminal domain (Table 1). Pharmacologically, they are the endogenous ligands of the G-protein-coupled receptor termed UT. Both peptides and receptor have been identified in several human tissues including brain, lung, heart, pancreas and kidney as well as vasculature, and until recently they were thought to exert redundant biological activity. More recently, evidence suggested that UII and URP might exert common but also divergent physiological actions.
Previous structure-activity relationship (SAR) studies have highlighted the critical role played by the intracyclic residues, identical in UII and URP sequences, as well as the disulfide bridge. More specifically, the critical role of the Trp-Lys-Tyr (WKY) triad both in the recognition and the activation process has been brought to the forefront. Indeed, replacement of Lys in either UII or URP with ornithine generated antagonists of the urotensinergic system[5,6] whereas the substitution of the Tyr residue in UII with a mono- or a di-iodo tyrosine led to a full and partial agonist respectively.[6,30] Inversion of configuration of the Trp residue in UII or URP resulted in a differential participative effect of this residue in these structures.[7-8]
TABLE 1Comparison of the primary structure of U-II and URP.[2]SpeciesOriginSequenceU-IILampreybrainH-Asn-Asn-Phe-Ser-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 1) Fuguspinal cord cDNAH-Thr-Gly-Asn-Asn-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 2) SkatebrainH-Asn-Asn-Phe-Ser-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 3) Dogfishspinal cordH-Asn-Asn-Phe-Ser-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 4) Sturgeonspinal cordH-Gly-Ser-Thr-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 5) Paddlefishspinal cordH-Gly-Ser-Thr-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 6) GobyurophysisH-Ala-Gly-Thr-Ala-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 7) Zebrafish αurophysis cDNA,H-Gly-Gly-Gly-Ala-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OHspinal cord cDNA(SEQ ID NO: 8) Zebrafish βurophysis cDNA,H-Gly-Ser-Asn-Thr-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OHspinal cord cDNA(SEQ ID NO: 9) Sucker AurophysisH-Gly-Ser-Gly-Ala-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 10) Sucker BurophysisH-Gly-Ser-Asn-Thr-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 11) Carp αurophysis, spinalH-Gly-Gly-Gly-Ala-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OHcord cDNA(SEQ ID NO: 12) Carp β1urophysisH-Gly-Gly-Asn-Thr-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 13) Carp β2urophysisH-Gly-Ser-Asn-Thr-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 14) Carp γurophysis, spinalH-Gly-Gly-Gly-Ala-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Ile-OHcord cDNA(SEQ ID NO: 15) Flounderurophysis, urophysisH-Ala-Gly-Thr-Thr-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OHcDNA(SEQ ID NO: 16) TroutbrainH-Gly-Gly-Asn-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 17) GroupercDNAH-Ala-Gly-Asn-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 18) Frogbrain, spinal cordH-Ala-Gly-Asn-Leu-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OHcDNA(SEQ ID NO: 19) ChickencDNAH-Gly-Asn-Leu-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 20) Zebra finchpredictedH-Gly-Asn-Leu-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 21) Mousespinal cord cDNA<Gln-His-Lys-Gln-His-Gly-Ala-Ala-Pro-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Ile-OH(SEQ ID NO: 22) Ratspinal cord cDNA<Gln-His-Gly-Thr-Ala-Pro-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Ile-OH(SEQ ID NO: 23) Porcine Aspinal cordH-Gly-Pro-Thr-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 24) Porcine Bspinal cordH-Gly-Pro-Pro-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 25) CattlepredictedH-Gly-Pro-Ser-Ser-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 26) Monkeyspinal cord cDNAH-Glu-Thr-Pro-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 27) ChimpanzeecDNAH-Glu-Thr-Pro-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 28) Humanspinal cord cDNAH-Glu-Thr-Pro-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 29) URPZebrafishcDNAH-Val-Cys-Phe-Trp-Lys-Tyr-Cys-Ser-Gln-Asn-OH(SEQ ID NO: 30) Chickenspinal cord cDNAH-Ala-Cys-Phe-Trp-Lys-Tyr-Cys-Ile-OH(SEQ ID NO: 31) Mousebrain cDNAH-Ala-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH (SEQ ID NO: 32) Ratbrain cDNAH-Ala-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 33) HorsepredictedH-Ala-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 34) ChimpanzeepredictedH-Ala-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 35) Humanbrain cDNAH-Ala-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH(SEQ ID NO: 36)
Although sharing the same intracyclic core sequence, previous SAR studies have highlighted differences in their recognition and activation process. Indeed, inversion of the configuration of the Trp residue in UII, hUII(4-11), the smallest hUII equiactive fragment, or URP demonstrated a differential participative effect of this residue in these structures.[9] Introduced in hUII or hUII(4-11), it produced weak agonists, whereas the same substitution in URP produced a partial agonist that is able to completely abolished the UII-induced aortic ring contraction. Such surprising behaviour was also observed when the phenylalanine moiety is replaced with a cyclohexylalanine residue since this substitution generated an antagonist when inserted in the hUII(4-11) sequence but a full agonist in URP.
UII- and URP-associated actions are mediated by the activation of a specific G protein-coupled receptor, UT, which plays a seminal role in the physiological regulation of major mammalian organ systems, including the cardiovascular system.[2] As a matter of fact, urotensin II exerts potent haemodynamic effects[10], positive inotropic and chronotropic responses[11] and osmoregulatory actions[12], induces collagen and fibronectin accumulation[13,14], modulates the inflammatory response[15], plays a role in the induction of cardiac and vascular hypertrophy[16], causes a strong angiogenic effect[17], and inhibits glucose-induced insulin release[18]. Thus, the urotensinergic system has been linked to numerous pathophysiological states including atherosclerosis, heart failure, hypertension, pre-eclampsia, diabetes, renal and liver disease, variceal bleeding, ulcers, and psychological and neurological disorders.[1]
Recent evidence suggested that UII and its paralog peptide URP might exert common but also divergent physiological actions.[19,20] For instance, studies have reported a differential action for these two peptides on cell proliferation[19], and distinctive myocardial contractile activities[20]. In isolated ischaemic heart experiments, both peptides were able to reduce myocardial injury through creatine kinase (CK) reduction but only UII was able to reduce atrial natriuretic peptide (ANP) production.[20] Moreover, UII, but not URP, exerted a dose-dependent mitogenic activity on astrocytes. More recently, a differential transcriptional modulation upon UII or URP activation was observed in isolated heart nuclei.[21] Moreover, distinct pathophysiological roles for UII and URP in hypertension have been suggested.[22] Indeed, the mRNA expression of both UII and URP were up-regulated in the atrium of SHR rats when compared with age-matched WKY rats. However, the specific up-regulation of URP but not UII mRNA in aorta and kidney of SHR rats supports the idea that these peptides may act individually in this biological system.[22] Key questions remain regarding the specific role associated with each peptide in this system.
Over the past decade, development of non-peptide UT antagonists has allowed investigators to begin to delineate the (patho)physiological roles of the UII/UT system.[23] However, none of the existing antagonists (peptidic and non-peptidic) was designed to discriminate specific UII- or URP-associated actions.
The present specification refers to a number of documents, the content of which is herein incorporated in their entirety.